I think in many respects the table may be an over-simplification of lower-level detail eg it does not show if each of the concurrent threads are actually using the same IndexReader objects, IndexWriter objects or are even operating in the same process (I think I read that write.lock file enables an Index to be opened by more than one process)
I suspect many Lucene users are like myself and are keen to understand what the concerns are when trying to set up a server and provide it with an ongoing stream of new documents or changes. This table is trying to offer that high-level overview. One approach discussed previously is to simply have a read-only index serving multiple concurrent search requests and use a separate write-capable index to apply updates in a single-threaded mode - the updated index is then "hot-swapped" onto the search server. This avoids the issues related to read-update contention. If you are going to attempt to have just one index serving search requests and processing changes/additions then you need to manage some of the contention eg doc changes require a delete and a write and this requires careful synchronization because of the restrictions on IndexReader.delete while a IndexWriter is open. This level of detail may be too much to encapsulate in a simple table (BTW, how does your triangle alternative work?). You are right in that the table as it stands doesn't show thread safety. I think it shows Lucene's management of contention. The "N"s are actually areas of contention where Lucene doesn't synchronize access (ie blocking one thread until another finishes) and instead simply throws an exception. The user is forced to ensure this condition never occurs and must sequence these requests appropriately. All the "Y" points in the table show areas where Lucene is happy to process simultaneous requests and (hopefully!) is synchronizing access to resources that would otherwise corrupt the index. Cheers Mark -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
